[PATCH V2 1/2] mtd: add support for partition parsers

[Marek Vasut]

On 02/21/2017 01:40 PM, Rafał Miłecki wrote:
> From: Rafał Miłecki <rafal at milecki.pl>
> 
> Some devices have partitions that are kind of containers with extra
> subpartitions / volumes instead of e.g. simple filesystem data. To
> support such cases we need to first create normal flash partitions and
> then take care of these special ones.
> 
> It's very common case for home routers. Depending on the vendor there
> are formats like TRX, Seama, uImage

uImage is file format, not partition type. It's just a blob of data
(usually kernel) with small header, I don't think we should represent
the content of it as a partition.

> , WRGG and more. All of them are used
> to embed few partitions into a single one / single firmware file.
> 
> Ideally all vendors would use some well documented / standardized format
> like UBI (and some probably start doing so), but there are still
> countless devices on the market using these poor vendor specific
> formats.
> 
> This patch extends MTD subsystem by allowing to specify partition format
> and trying to use a proper parser when needed. Supporting such poor
> formats is highly unlikely to be the top priority so these changes try
> to minimize maintenance cost to the minimum. It reuses existing code for
> these new parsers and just adds a one property and one new function.
> 
> This implementation requires setting partition format in a flash parser.
> A proper change of bcm47xxpart will follow and in the future we will
> hopefully also find a solution for doing it with ofpart
> ("fixed-partitions").
> 
> Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
> ---
> V2: A totally rebased & refreshed version.
> ---
>  drivers/mtd/mtdpart.c          | 38 ++++++++++++++++++++++++++++++++++++++
>  include/linux/mtd/partitions.h |  7 +++++++
>  2 files changed, 45 insertions(+)
> 
> diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
> index ea5e5307f667..9a40c3ea384b 100644
> --- a/drivers/mtd/mtdpart.c
> +++ b/drivers/mtd/mtdpart.c
> @@ -363,6 +363,42 @@ static inline void free_partition(struct mtd_part *p)
>  	kfree(p);
>  }
>  
> +/**
> + * mtd_parse_part - parse MTD partition with a matching parser
> + *
> + * Some partitions use a specific format to describe contained subpartitions
> + * (volumes). This function tries to use a proper parser for a given format and
> + * registers found (sub)partitions.
> + */
> +static int mtd_parse_part(struct mtd_part *slave, const char *format)
> +{
> +	struct mtd_partitions parsed;
> +	const char *probes[2];
> +	int i;
> +	int err;
> +
> +	probes[0] = format; /* Use parser with name matching the format */
> +	probes[1] = NULL; /* End of parsers */
> +	err = parse_mtd_partitions(&slave->mtd, probes, &parsed, NULL);
> +	if (err)
> +		return err;
> +	else if (!parsed.nr_parts)
> +		return -ENOENT;
> +
> +	for (i = 0; i < parsed.nr_parts; i++) {
> +		struct mtd_partition *part;
> +
> +		part = (struct mtd_partition *)&parsed.parts[i];
> +		part->offset += slave->offset;
> +	}
> +
> +	err = add_mtd_partitions(slave->master, parsed.parts, parsed.nr_parts);
> +
> +	mtd_part_parser_cleanup(&parsed);
> +
> +	return err;
> +}
> +
>  /*
>   * This function unregisters and destroy all slave MTD objects which are
>   * attached to the given master MTD object.
> @@ -724,6 +760,8 @@ int add_mtd_partitions(struct mtd_info *master,
>  
>  		add_mtd_device(&slave->mtd);
>  		mtd_add_partition_attrs(slave);
> +		if (parts[i].format)
> +			mtd_parse_part(slave, parts[i].format);
>  
>  		cur_offset = slave->offset + slave->mtd.size;
>  	}
> diff --git a/include/linux/mtd/partitions.h b/include/linux/mtd/partitions.h
> index 06df1e06b6e0..2787e76c030f 100644
> --- a/include/linux/mtd/partitions.h
> +++ b/include/linux/mtd/partitions.h
> @@ -20,6 +20,12 @@
>   *
>   * For each partition, these fields are available:
>   * name: string that will be used to label the partition's MTD device.
> + * format: some partitions can be containers using specific format to describe
> + *	embedded subpartitions / volumes. E.g. many home routers use "firmware"
> + *	partition that contains at least kernel and rootfs. In such case an
> + *	extra parser is needed that will detect these dynamic partitions and
> + *	report them to the MTD subsystem. This property describes partition
> + *	format and allows MTD core to call a proper parser.
>   * size: the partition size; if defined as MTDPART_SIZ_FULL, the partition
>   * 	will extend to the end of the master MTD device.
>   * offset: absolute starting position within the master MTD device; if
> @@ -38,6 +44,7 @@
>  
>  struct mtd_partition {
>  	const char *name;		/* identifier string */
> +	const char *format;		/* partition format */
>  	uint64_t size;			/* partition size */
>  	uint64_t offset;		/* offset within the master MTD space */
>  	uint32_t mask_flags;		/* master MTD flags to mask out for this partition */
> 


-- 
Best regards,
Marek Vasut